Skip to main content

Echo Provider

The Echo Provider is a simple utility provider that returns the input prompt as the output. It's particularly useful for testing, debugging, and validating pre-generated outputs without making any external API calls.

Configuration

To use the Echo Provider, set the provider ID to echo in your configuration file:

providers:
- echo
# or
- id: echo
label: pass through provider

Response Format

The Echo Provider returns a complete ProviderResponse object with the following fields:

  • output: The original input string
  • cost: Always 0
  • cached: Always false
  • tokenUsage: Set to { total: 0, prompt: 0, completion: 0 }
  • isRefusal: Always false
  • metadata: Any additional metadata provided in the context

Usage

The Echo Provider requires no additional configuration and returns the input after performing any variable substitutions.

Example

providers:
- echo
- openai:chat:gpt-4o-mini

prompts:
- 'Summarize this: {{text}}'

tests:
- vars:
text: 'The quick brown fox jumps over the lazy dog.'
assert:
- type: contains
value: 'quick brown fox'
- type: similar
value: '{{text}}'
threshold: 0.75

In this example, the Echo Provider returns the exact input after variable substitution, while the OpenAI provider generates a summary.

Use Cases and Working with Pre-generated Outputs

The Echo Provider is useful for:

  • Debugging and Testing Prompts: Ensure prompts and variable substitutions work correctly before using complex providers.

  • Assertion and Pre-generated Output Evaluation: Test assertion logic on known inputs and validate pre-generated outputs without new API calls.

  • Testing Transformations: Test how transformations affect the output without the variability of an LLM response.

  • Mocking in Test Environments: Use as a drop-in replacement for other providers in test environments when you don't want to make actual API calls.